Studies will be continued on the mechanisms of action of hormonal and other regulatory factors in certain insect systems. The major emphasis will be on the mode of action of juvenile hormone in inducing synthesis of vitellogenin (yolk protein precursor) in fat body of locusts (Locusta migratoria), including changes in subcellular structure and the participation of specific kinds of RNA. A second project is analysis of the regulation of glycogen phosphorylase activity in silkmoth fat body, where activation by cold leads to net production of glycerol from glycogen. A third investigation is the regulation and role of the high level of cyclic GMP that is found in the accessory reproductive gland of the male house cricket. Bibliographic references: A.M. Fallon and G.R. Wyatt. An improved assay for cyclic GMP using an insect binding protein. Anal. Biochem. 63, 614-619 (1975). G.R. Wyatt. Hemolymph in insects and arachnids - some biochemical features. In "Invertebrate Immunity" (K. Maramorosch and R.E. Shope, ed.) Academic Press, New York. pp. 225-240 (1975).